Polyphenylene ether is useful as a resin material for molding because of its good mechanical and electrical properties. However, it has poor oil-resistance. In order to solve this disadvantage, it is known that polyphenylene ether can be blended with polyamide which is resistant to oil (see, for example, Japanese Patent Laid-Open No. 16525/1981). The resulting composition exhibits improved oil resistance as compared to polyphenylene ether alone. However, polyphenylene ether and polyamide show poor compatibility with each other and, accordingly, properties intrinsic to these two resins, e.g., the excellent mechanical properties, are not fully exhibited when the resins are combined.
Finholt (U.S. Pat. No. 3,379,792) disclosed polymer blends wherein the processability of polyphenylene ether resins may be improved by blending with from 0.1 to 25% by weight of a polyamide. However, the advantages of the Finholt invention are limited by the fact that when the concentration of the polyamide exceeds 20% by weight, appreciable losses in other physical properties result. Specifically, there is no, or at best poor, compatibility between the polyphenylene ether and the polyamide such that phase separation of the resins occurs on molding or the molded article is inferior in mechanical properties.
Compatibility between the polyphenylene ether and polyamide phases can be improved by the addition of any of several compounds referred to as compatibilizers and the resin product may be referred to as compatibilized polyphenylene ether-polyamide. It is believed that the compatibilization may be accomplished by chemical or physical means, or both, and generally indicates a thorough dispersion of one resin in the other.
Ueno et al. (U.S. Pat. No. 4,315,086) disclosed polyphenylene ether blends having improved mechanical resistance without a loss of other mechanical properties by blending therewith a polyamide and a specific compound selected from the group consisting essentially of (A) liquid diene polymers, (B) epoxy compounds and (C) compounds having in the molecule both of (i) an ethylenic carbon-carbon double bond or carbon-carbon triple bond and (ii) a carboxylic acid, acid anhydride, acid amide imide, carboxylic acid ester, amino or hydroxy group.
Kasahara et al. (EP No. 46040) disclose the use of a copolymer comprising units of a vinyl aromatic compound and either an alpha, beta-unsaturated dicarboxylic acid anhydride or an imide compound thereof as a modifier to an impact resistant polyphenylene ether-polyamide blend for improved heat resistance and oil resistance.
Avcock et al. (U.S. Pat. Nos. 4,600.,741 and 4,642,358) disclose the use of an acyl functional compatibilizer, preferably the reaction product of polyphenylene ether with trimellitic anhydride acid chloride, for compatibilized for polyphenylene ether-polyamide blends. Other suitable compatibilization techniques are discussed below.
It is an object of the present invention to enhance the melt flow characteristics of such compatibilized PPE-polyamide composites by incorporation therein of certain effective carboxylic acids and related compounds.